IR ablateable waterless offset printing plates, also termed IR ablateable driographic printing plates, are well known in the art. They typically include, in order, a substrate, e.g. a polyester film, an intermediate oleophilic Infra Red (IR) radiation absorbing layer and a top oleophobic layer.
Offset printing plates, including waterless offset printing plates are selectively exposed to radiation in order to expose a latent image thereon, the image subsequently is selectively colored during printing with oil based inks, typically the four process inks Cyan, Magenta, Yellow and Black (CMYK) inks.
In most IR sensitive driographic plates, the latent image is recorded by ablating the top oleophobic layer and therefore during printing, the oil based inks are repelled by the areas of the top oleophobic layer which have not been ablated during imaging and are not repelled by the oleophilic absorption layer and the substrate revealed in the ablated areas.
Typically, the top ablateable oleophobic layer is composed of silicone (polysiloxane) or a mixture of silicones cross-linked by cross-linking agents deposited on the plate from a solution dissolved in an organic solvent.
For example, naphtha was described as the solvent employed for producing the top ablateable oleophobic layer using one silicone composition in U.S. Pat. No. 5,378,580 to Leenders and using a mixture of silicone solutions with cross linking agents in U.S. Pat. No. 5,310,869 to Lewis et al.
In the prior art, the IR absorption layer of driographic printing plates have been also produced employing organic solvents. For example, published PCT application GB93/01413 to Gutes et al describes the use of a water-alcohol mixture, for producing the IR absorption layer.
Generally speaking, since organic solvents are used in preparing prior art driographic printing plates, the plates are not environmentally friendly.